In general, a method, which has been known as a method for connecting a core wire of a wire rod to a substrate such as a terminal, includes: winding a wire rod having an insulating coating formed on the periphery of the core wire around a substrate such as a terminal, followed by soaking the wire rod in a solder tub, removing the insulating coating from the wire rod by melting the insulating coating under the melting heat of the solder; and adhesion-fixing copper or the like, which is the core wire of the wire rod, to the substrate such as the terminal.
Miniaturization and operating environment of electronic apparatus have become severe in recent years. The operating environment of electronic components, such as a coil incorporated therein, has also become extremely severe. Therefore, the high heat resistance of the electronic component itself has been also requested simultaneously with miniaturization of electronic components. In order to respond to such demands, for example, there is no way to avoid the use of a wire having an insulating coating with high heat resistance on the periphery of its core wire and the use of a thin wire as a wire rod for the miniaturization of electronic components. However, when connecting a wire rod to a substrate such as a terminal, mechanical removal of an insulating coating tends to cause wire disconnection. On the other hand, in the case of removal of the insulating coating of a wire rod by melting with the melting heat of solder, there is a problem of difficulty in placing a miniaturized substrate into a solder tub.
In recent years, therefore, other methods have been proposed, where an insulating coating on the periphery of a core wire of a wire rod is delaminated therefrom by burning with laser beam irradiation, and simultaneously the core wire of the wire rod is connected to a substrate such as a terminal.
For instance, Japanese Laid-Open Patent Publication No. 3-155300 (JP 3-155300 A) discloses a method including: previously applying solder to a lead wire installed in a coil bobbin to form a solder layer; winding a wire rod around the lead wire, the wire rod being pulled out from a coil component and covered with an insulating coating; melting the solder layer portion by laser beam irradiation thereon; and burning an insulating coating with the melting heat of solder to remove the insulating coating, while connecting the wire rod to the lead wire. This method allows soldering operation to be flexible even if electronic components are miniaturized, compared with other conventional methods where soaking in a solder tub is employed for connection.